It is known to provide layer systems upon an appropriate substrate, such as a silicon wafer, of materials having electrical, electronic or optical characteristics which enable them to be used for electronic, electro-optical, magnetic and optical components in communications and other systems. The layers generally include at least one semiconducting layer and may be composed of semiconductive, metallic and electrically insulating materials. A stack of layers in such a system can include at least two layers of which one, for example, the lower layer or the one closest to the substrate, may be epitaxially grown and a monocrystalline layer upon which the second layer of the pair is deposited.
To fabricate such layer systems and structures, practically all of the techniques which have been developed heretofore for thin layer fabrication, layer growth and the formation of layer stacks at appropriate temperatures and under well-controlled deposition conditions may be used. In particular, we may mentioned molecular-beam epitaxy (MBE), ultrahigh vacuum evaporative deposition (UHV) and chemical vapor deposition (CVD) techniques.
In the past, however, for the formation of different layers on one another, the approach has been to first deposit one component (on a substrate or upon a previously-formed layer) and then to deposit a discrete layer of the next component so that both components are deposited separately.
This approach results in the formation of a multilayer system with sharply distinguishable layers. When, however, not only the first of these layers, for example, the lowermost layer, is to be composed of a monocrystalline structure, but also the upper layer deposited thereon has to be a monocrystalline layer, grown of the latter on an intermediate layer, which does not have a matched monocrystalline structure, is difficult to achieve, if not impossible.
For example, it has not hitherto been possible to provide a buried monocrystalline silicide of high quality on (100) Si by the mentioned techniques. Overgrowing of Si on the monocrystalline silicide, to provide embedded conductive pathways or special components for electronic or electro-optical purposes has been problematical heretofore.
The formation of buried monocrystalline silicides of relatively good quality, especially upon (100) Si has been achieved heretofore only by means of high-dose implantation techniques (A. E. White, K. T. Short, R. C. Dynes, J. P. Garno and J. M. Gipson, Appl. Phys. Lett. 50 (1987) 95).
Industrially applied methods for producing embedded insulation layers (SiO.sub.2 layers in Si) can utilize high-dose implantation of oxygen ions in silicon wafers (K. Izumi, M. Doken and H. Arigoshi, Electron. Lett. 14 (1978) 593). These processes, however, are extremely expensive and cannot avoid relatively high dislocation densities in silicon and other lattice defects resulting from the implantation.